1. Field of the Invention
This invention relates to tools for use with fastening arrangements and associated fastening kits.
2. Description of Related Art
There are many situations where it is required to connect together two items either permanently or semi-permanently and where there is access to one side only of the assembly. Examples include the attachment of panels or plates to underlying frames or supports in structures such as aircraft, ships, cars, etc. Arrangements such as captive bolts, blind rivets, rivet nuts etc., may be used in such applications. There are however disadvantages with such arrangements. For example, with rivets and captive nuts, the surface of the panel is interrupted by the head of the rivet or bolt. This interruption increases aerodynamic drag and, if the panel itself otherwise has a low radar signature, considerably increases the radar signature. In addition the exposed head of the rivet or bolt which is normally connected at its other end to a metal support structure, renders the head of the bolt or rivet susceptible to lightning strike.
Accordingly, parent application Ser. No. 09/381,268, now U.S. Pat. No. 6,398,450B1discloses a fastener arrangement for connecting together two members, the arrangement including a first component for association with a first of the members, and a second component for association with the second of the members.
The second component includes a retention element of shape memory material configurable between a closed state in which it engages the first component to retain it, and an open state in which the first component may be withdrawn from the second component. A closure element is adapted in use to co-operate with the retention element during fastening of the arrangement to deform the retention element from its open state to its closed state.
This arrangement therefore makes use of the recovery properties of a shape memory material to reconfigure between a closed state and an open state.
The provision of a closure element facilitates the application of an external force to deform or swage the shape memory retention element around the first component.
The first component preferably includes a head means for engaging said first member and a shank means comprising an engagement region for engaging said second component, said engagement region including a region of non-constant cross section including an abutment or shoulder region for co-operation with an associated abutment region on said retention element. In one arrangement, said region of non-constant cross section is tapered in the direction away from said head means. Many geometries are possible. In particular, it should be noted that, although in the preferred embodiment, the second component fits around the end of the first, it would be possible to have an arrangement in which the second component was deformed to fill a recess or bore within the first component.
Preferably, the retention element is made of a heat recoverable shape memory metal alloy. The retention element is preferably formed such that, when in said closed state, on heating to a temperature equal to or greater than a predetermined recovery temperature, the retention element tends to recover to said open state (assuming that the retention element is otherwise unencumbered).
To allow said retention element to be heated by the application of a coil or tool remote therefrom, the retention element is preferably made of an inductive metal material, whereby said tension element may be heated by the application of an electric field.
It will be appreciated that, in the preferred embodiment, the closure element needs to be moved into and out of engagement with the retention element to open and close it. A reasonable amount of force may need to be provided and this ideally is provided without direct mechanical application. Thus the closure element is preferably formed of a ferro-electric material whereby it may be urged into or out of engagement with said retention element by the application of an external magnetic field.
According to one aspect of this invention, there is provided a tool for use in securing or releasing a fastener arrangement, which has a first component and a second component, the second component including a retention element of shape memory material adapted to be deformed releasably to retain the first component and a closure element for cooperating with the retention element to deform it.
The tool includes a magnetic field producing means for producing magnetic field of a given polarity for urging the closure element in a direction tending to cause the retention element to change from its open state to its closed state, a magnetic field producing means for producing a magnetic field for urging said closure element away from cooperation with the retention element, and a heating coil for applying at least one of inductive heating and electrical heating of the retention element.
The magnetic field producing means may include a common magnetic coil means, energizing means for energizing the coil means, and reverse switch means for changing the polarity of the energization. The magnetic field producing means conveniently includes electrical storage means and cycle control means for supplying to the coil means a short high intensity pulse thereby to produce a short, high intensity magnetic impulse.
The tool may include a further coil means for generating a magnetic field for rendering the closure element magnetic.
According to another aspect of this invention, there is provided a tool for use in securing or releasing a fastener arrangement, which has a first component and a second component, the second component including a retention element of shape memory material adapted to be deformed releasably to retain the first component and a closure element for cooperating with the retention element to deform it.
The tool includes an electromagnetic coil for producing a magnetic field of a given polarity for urging the closure element in a direction tending to cause said retention element to change from its open state to its closed state, an electromagnetic coil for producing a magnetic field for urging the closure element away from cooperation with the retention element, and a heating to coil for applying at least one of inductive heating and electrical heating to the retention element.
The electromagnetic coils may include a common coil, and associated therewith an energy force for energizing the coil, and a reverse switch for changing the polarity of the energization. The electromagnetic coil may have associated therewith a cycle control circuit for supplying to the coil a short high intensity pulse thereby to produce a short, high intensity magnetic impulse. The tool may further include an electromagnetic coil for generating a magnetic field for rendering the closure element magnetic.
In a further aspect, this invention provides a tool for use in securing or releasing a fastener arrangement, which has a first component and a second component, the second component including a retention element of shape memory material adapted to be deformed releasably to retain the first component and a closure element for co-operating with the retention element to deform it.
The tool includes electromagnetic means operable to generate an electromagnetic field for applying to an object in the field a force in at least one of two opposed directions, and electrical heating means for generating at least one of electrical heating and inductive heating in a region adjacent the tool for heating an object in the region.
In another aspect, there is provided a method of connecting together two members, which method includes providing a fastening arrangement including a first component for association with a first of the members and a second component for association with the second of the members. The second component includes a retention element of shape memory material configurable between a closed state in which it engages the first component to retain it and an open state in which the first component may be withdrawn therefrom. The method further includes bringing together the two members, assembling the first component and the second component with the retention element initially in an open state, and urging a closure element against the retention element to change it to its closed state, thereby connecting the members.
Preferably the retention element is moved to its closed state by means of a closure element. Preferably, the closure element is moved between the fastened or relaxed states by means of an electrical and/or magnetic field. For release of the fastening, the retention element is preferably heated to a temperature equal to or greater than its recovery temperature. Heating may conveniently be by means of a high frequency electromagnetic field, or an electrical current.
Whilst the invention has been described above, it extends to any inventive combination of the features set out above or in the following description.